Method of casting concrete building elements



' NUV- 28, 1950 J. E MGCLELLAN ETAL uE'rHon oFfcAsTIN'G coNcRE'rEBUILDING Emu-ms med um 25, 194s 2 Sheets-Shee't 1 Nv. 28, 1950 J. E.MGCLELLAN E-rAL 2,531,576

HETHOD 0F CASTING CONCRETE BUILDING ELEHENTS .Z'n van 771712.5-

Jam 55.231777: .CIEL/'an Ja k .H l :7.27 ald UNITED lSTM-lss PATENTOFFICE 2,531,573 Y l A mon F CASONETE BUILDING tres: McClellan fInccorporation of California Calif., a

application Marsh as, 194s, serial No. 17.078 1 (ci. :as-155) Thisinvention isconcerned generally with the construction of buildings bythe prefabrication of concrete building elements.

More particularly. the invention includes an improved and simplifiedmanner of molding concrete building elements which is particularlyadapted for use at the building site.

The invention includes also various fittings and Procedures which insuitable combination lead to great economy in construction and toimproved operation generally.

The invention. together with its further objects and advantages, will bebest understood from the following detailed description of certainpreferred embodiments. That description and the accompanying drawingsare illustrative, and are not intended to limit the scope of theinvention, which is defined by the appended claim. The drawings form apart of the following description, and: f

Fig. l is a fragmentary plan of typical panel form constructed on acoated concrete base, ready for pouring;

Fig. 2 is a fragmentary vertical sectiontaken on line 2--2 of Fig. l; n

Fig. 3 is a section similar to Fig. 2. but showing the concrete pouredand set; and

Fig. 4 is a section similar to Fig. 3, but'showing a second panel formin position on the ilrst panel.

An important feature of the invention is the method of prefabricatingconcrete building elements such as beams and wall panels by pouring themin forms, one wall of which is the face of a previously preparedconcrete element. As an illustrative example of the method, Figs. 1 and2 show a form l! for a wall panel, constructed directly on the surfaceoi a concrete floor slab Il, which itself has been formed in any usualmanner, for example by pouring concrete directly on a suitably gradedearth foundation 32. After the concrete door slab has partially set andbefore construction of foi-m30, the entire upper surf face of the floorslab is coated with a suitable liquid sealing composition. Thiscomposition is of such a nature that it forms on the concrete surface asubstantially water impermeable layer it preferably covers the entiresurface of concrete slab 3l on which form 30 is to be constructed. Thesealing layer then assists the curing of the floor slab, which continuesduring lconstruction of the superimposed panels.

After the coated concrete oor has sufciently set, which may typicallyrequire 24: hours, the panel form 30- is constructed directly upon it.That form comprises in general a frame 35 outlining the panel edges andprojecting upward from oor 3| a distance equal to the panel thickness.If the panel is to be four inches thick, as is typically the case, 2 x 4lumber, finished accurately to dimension is preferably used for the formframe.

If a window or door frame is to be set into the panel, the requiredpanel aperture can be blocked out with form lumber, and the actualwindow frame or door frame set in place after the panel has beencompleted and erected. However, particularly with window frames, it isgenerally preferred to set the complete frame directly in place as apart of form 30, as indicated at 31, blocking it in as with form members38 to complete the definition of the panel aperture. Any desired edgesection can be obtained at the panel edge or in the concrete surroundingthe window (or door) aperture by introducing appropriately formedmolding strips in the form. as shown typically at 40. `In practice thewindow frames 31, preferably of metaLvare blocked in advance with formmembers 3B of suitable section, which are secured temporarily to theframes as by braces 39. In constructing the panel form. the blockedframe is then merely laid on iioor 3| and secured inthe correct-locationwith respect to form frame 35.`

Form frame 35, blocked window frame 31, and any other members whichdefine boundaries of the panel mustbefirmly anchored in place 'on iioor3l and tied down to it,` so that the concrete will not flow under themand lift them from position. Typical anchoring means are cross braces44, blocks 46 and the bolts 42 secured in suitable fittings 43, whichmay be set in advance for this purpose in floor 3|, either flush withits surface or slightly below it. After fittings 43 have served theirpurpose they are preferably plugged with concrete. yielding a smoothfinal iioor surface. Bolts 42 may pulldown cross braces 44, eitherdirectly orthrough auxiliary connections such as straps 45. Alternativeanchoring means are shown in Fig. 4 in the form of weights such as sacks41 of sand or the like piled on cross braces 44. v

Reinforcing iron 50. `5| is set in form SII, tied form 30; and pickupfittings are shown at |65,

welded to reinforcingiron in the form. Channel reinforcing similar tocorner angle 55 may be used along any panel edges desired, but is notordinarily required. Welding plates |80 are preferably inserted afterpouring, and are brought accurately flush with the surface of the wetconcrete.

As the wet concrete mix is poured into the form it is vigorouslyvibrated by any suitable tamping means, preferably a power drivenflexible vibrator, to insure a solid and uniform fill. The upper face isleveled in the usual manner, with reference to the upper edge of formframe 35, and is finished to any desired texture. After the concrete hastaken an initial set, anchoring ties 42, 44 may be removed, leaving thecomplete concrete panel 58 lying directly on the coated concrete floor3| and still surrounded by form 30, as in Fig. 3.

A second concrete element can now be cast directly on panel 58. Forexample, a second concrete panel, preferably of equal or smaller size,can be cast on the face of the rst panel. Fig. 4 shows a form 60 forsuch a second panel in place on panel 58. As illustrated, the outerboundary of the second panel coincides with that of the first along theright hand edge (as seen in Fig. 4l and lies inside that of the firstalong the left hand edge. The second panel has a window aperture,defined by blocked window frame 61, which is of such size and positionthat it includes all of the window aperture of the first panel, and, inthe present instance, extends beyond that aperture to the left in Fig.4. Similarly, the relative panel dimensions normal to the plane of Fig.4 are understood to be such that all parts of the. second panel liedirectly above nished panel 58.

Before a form such as 60 is constructed on panel 58, the upper face ofpanel 58 is coated with the sealing preparation, as has already beendescribed for preparing floor 3| for the casting of the rst panel. Sucha coating is shown schematically at 63 in Fig. 4. The construction ofthe second panel form then proceeds substantially as described for thefirst panel form, except that the upper face of first panel 58 performsthe function previously performed by the surface of oor 3|. The secondpanel frame 65 and blocked window frame 61 may conveniently be anchoredeither to floor 3|, for example by bolts 42, cross braces 44 and straps45, as described above; or directly to the first panel form 30, which ispreferably still in place. The latter type of anchor is indicated at 66.

After the second panel has been poured in form 60 and has partially set,additional panels i provided they are of suitable dimensions) can beconstructed successively `on top of it. Thus a stack of panels isproduced, as shown in Fig. 4, separated only by the sealing layerdeposited on each surface before the following panel is poured. Thefinal upper surface is preferably also sealed in the same manner toimprove curing. The form frames may be left in place around the paneledges during whatever time is required for adequate curing of the panelstack, and are generally stripped ofi just before or during theoperation of erecting the panels.

The number of panels in a stack depends in practice upon the shapes ofthe individual panels and also upon the relative area of the concretefloor 3| as compared to the total area of the panels or other concreteelements which are to be formed. Panels for the entire wall surface of asmall commercial building, for example, can ordinarily be cast'on thefloor of the building itself without requiring more than two or threepanels in a stack. On the other hand, if roof panels are also to be castin the same manner, it is sometimes convenient to cast as many as fiveor six panels in a stack. This sometimes means designing the variouspanels so that they will stack effectively, the area of each successivepanel being contained Within the area of the panel upon which it isconstructed. That condition need not be precisely fulfilled, since ifnecessary the area of a panel can be extended by suitable blocking orframing in order to permit a larger panel form to be constructed uponit. But such a procedure is preferably avoided for the sake of economyand speed in construction.

After all the panels of a stack have been poured in the mannerdescribed, typically requiring about one day for each panel in thestack, all the panels and the concrete floor on which they are supportedare allowed to complete the setting process and to cure, usually forseveral days. During curing, the water impermeable layer 33 on thefloor, the layers 63 between successive panels, and a final similarlayer, which is preferably applied to the exposed surface of the toppanel of the stack. assist the curing process by retardinq evaporationof water from the exposed concrete surfaces and by preventing migrationof water from one concrete element to another across their contactingfaces.

After the panels have suflicientlv cured, they are lifted upsuccessively from the floor or from the top of the stack in which theywere cast, and set in position to form the building. A convenient meansof handling panels is a conventional portable crane, which can operatefrom outside the building or can work on the same floor on which thepanels have been formed. An advantage of the type of panel formdescribed above is that the panels are directly and firmly supported onthe floor so that there is no tendency for them to be cracked if thecrane runs over a panel. It is only necessary to block the panel edgesto prevent local chipping of the panel. Accordingly, the crane canoperate quite freely on a floor that is largely covered by panels, solong as the stacks are not too high.

Not only wall panels, but structural elements of various other kinds canalso be cast on a previously prepared concrete surface. For example,structural columns, beams, or unitary frames including both columns andbeams can be poured in this manner. and in most cases this method leadsto great economy in labor, form lumber and construction time.

In both structural forms and panels, reinforcing iron can be made toprotrude from the finished member in nearly any direction to serve asdowels, openings being cut in the form members when necessary, asindicated at 50a, the only exception being that face of the member whichrests on the coated concrete base during Pouring. v v

In forming both panels and other members in accordance with theinvention, the face which is cast uppermost can very readily be finishedto any desired texture, whereas when the members are poured in positionwith conventional form construction that is difficult or evenimpossible. The under face can also be given certain textures bycovering the concrete base with a layer of suitable material, the upperface of which carries the desired texture. However, that procedure tendsto sacrifice some of the potential simplicity and economy of the method.

The success of the process described above depends largely upon thepossibility of producing on the concrete surface which is to become aform wall a sealing layer having satisfactory properties. A primaryrequirement of such a layer is that it should prevent the formation of abond between the concrete of the form wall and the concrete which ispoured in the form, even after the latter concrete has partially orwholly set. An important additional result of using water-imperviouscoatings in accordance with the invention is that loss of water iswholly or largely prevented both from the concrete of the/form wall andfrom the concrete poured in the form. This has the well-known advantageof improving the curing of the concrete.A Indeed, the function offorming a water seal on a concrete surface is so important for propercuring that a special sealing layer is frequently applied solely forthat purpose. When the present method is employed, that function isperformed by the coatings 33, 63, and no special processing is necessaryto insure proper curing.

The most satisfactory compositions for the purposes outlined above havebeen found to be substances which are water insoluble and which undernormal conditions are either solids of very low tensile strength, such,for example, as paraffin wax and resin; highly viscous and non-volatileorganic fluids, such, for example, as heavy petroleum residues orvegetable oils. Substances of these types can be used alone or incombination. Certain synthetic resins are useful provided they do notbecome hard when exposed to air, or provided they are combined withother substances which prevent such hardening. The coating compound ismost satisfactorily applied in solution in any suitable volatile cutback material in which it is soluble, for example a volatile petroleumsolvent. The solvent serves as a vehicle of relatively low viscosity,and evaporates after application, leaving a uniform layer of the sealingcompound on the concrete surface. The substances described above canalso be applied to the concrete surface in the form of a stabilizedemulsion in water, using some suitable emulsifying agent such as soap.

It has been found that water-impervious coatings of the type described,which characteristically produce a weak bond between the concrete masseswhich they separate, are even more effective in preventing such a bondwhen they contain a quantity of some finely divided solid which is inertwith respect to the other ingredients present. Examples of suchmaterials are powdered talc, graphite, or any finely ground micaceousmaterial. Presumably the presence of such inert materials furtherweakens the already small tensile strength of the coating, and thusinhibits any effective bond formation. While the addition of powderedinsoluble solids is preferred, it is not necessary to the successfulcarrying out of the method.

As will be appreciated, the coating compositions useful in thisinvention are easilyseparable from the concrete layers upon which theyare applied by conventional means.

For lifting the larger panels, which may measure more than 20 feetsquare and weigh roughly 10 tons, a very considerable force isoccasionally needed to break the panel loose from its supportingsurface. To distribute that pickup force reasonably uniformly over thepanel area, pickup fittings are preferably placed some distance in fromthe edges of such panels. Furthermore, a flush type of fitting isdesirable, both to avoid disilguring the finished wall, and to maintainthe upper face of the poured panel as an unbroken surface on which toconstruct superposed panels.

Figs. 1, 2 and 3 illustrate a type of pickup tting presently preferred,which meets the outlined requirements for large panels and yet is simpleand economical to produce and convenient in use. Fittings of this typeare shown during various steps of the pouring process in Figs. 1-4. Eachpickup unit |65 comprises one or more internally threaded sleeves, equalin length to vthe panel thickness, and widely flanged at one end. Eachsleeve is enclosed by transverse bars |61 which are rigidly connected toit in bearing contact with the inner axial face of the ange.

In the particular embodiment illustrated, the

flanged and threaded portion of the sleeve is provided by a large nut|66. The remainder of the sleeve |68 is of relatively light stock,preferably tack welded to one face of the nut coaxially with itsthreaded hole. The two heavy bars |61 of reinforcing iron are weldedacross the same face of the nut on opposite sides of the sleeve |68.When two or more nuts are used in a unit, they are spaced along the bars|61 at intervals of roughly one foot, with their sleeves |68 pointing inthe same direction. 'I'he overall length of sleeve |68 and nut |66 ischosen approximately equal to the thickness of the concrete panel to beformed.

The pickup unit is placed at the required location in the panel formbefore concrete is poured, with the exposed face of each nut |66preferably directly on the form floor 3| and the upper end of eachsleeve |68 in the plane of the upper panel face. The depth of the nuts|66 is sufficient to raise bars |61 a suitable distance above the formfloor, and yet leave the greater part of the panel thickness above thebars. In particular, the regular reinforcing iron (50, 5| in Figs. l-4)of the panel lies above bars |61 in position to distribute mosteffectively any lifting strain applied to nuts |66. The sleeves |68 areplugged during pouring, for example by the temporary insertion of bolts|10 (Fig. 3), and serve to keep the threads of nuts |66 clear of cementand thus to provide access to the nuts from the upper panel face. If thecombined length of a nut |66 and sleeve |68 is somewhat less than thepanel thickness, the entire assembly can be raised above the form floor3| by merely screwing bolts |10 into the nuts until they protrude therequired amount from the lower faces of the nuts and act as supportinglegs. The protruding bolt ends do not become bonded to the concrete ifthey are removed as soon as the concrete has taken an initial set. Whileit is preferred to fasten sleeves |68 rigidly to nuts |66 to form ineffect a unitary flanged sleeve, the sleeve members |68 may be merelypositioned over the nuts and temporarily held in place by bolts whilethe concrete is poured and set. Any tendency of the wet concrete to leakbetween sleeves |68 and either nuts |66 or the heads of bolts |10 canthen be prevented by applying heavy grease to those joints. When asecond panel is to be poured on top of the first, sleeves |68 in thelower panel pickup fittings are temporarily plugged flush with the panelface, as with corks.

Two pickup units |65 are ordinarily used in each panel, approximatelysymmetrically spaced from a vertical line through the computed center ofgravity of the panel (when in final position. In wall panels the pickupumts are spaced above a horizontal line through the center of gravity,so that when lifted the panel will naturally hang in a nearly verticalplane; but (at least in large panels) the fittings are perfectly spacedwell in from what will be the upper edge of the panel to distribute thepickup forces more uniformly. In wall panels, bars |61 are preferably sooriented in the panel form that they will be horizontal when the panelis in its final position in the wall.

An advantage of pickup fittings of the type just described is that afterthe panels have been secured in position and bolts |10 removed, ,thefitting is already flush with the panel face, and can readily be madealmost invisible merely by plugging sleeve |68, as with concrete.

In general, suitable fittings are set into the concrete of the panelsfor anchoring them in final position in the building. Those fittings areof various sorts, depending primarily upon the function the panel is toserve and upon the neighboring structural elements to which it is to besecured. Ordinarily the vertical edges of a wall panel are anchoreddirectly to the columns of the building framework. Preferred means forsecuring concrete panels to steel members comprise weld plates |80, setilush in the panel face as illustratively shown in Figs. 3 and 4. Weldplates |80 are typically of steel 1A inch thick and about three inchessquare, and are anchored in the concrete of the panel by any suitablemeans, such as the head portion of a bolt or a curved anchoring rod, asindicated at |8|, buttwelded to the inner face of the plate. The moreelaborate anchoring means |61 used for the pickup fittings |65 describedabove are not necessary here, since the required strength of weld plates|80 is not abnormally great. Weld plates |80 are preferably set in thefreshly poured concrete flush with its upper surface, as indicated inFig. 8. An advantage of the type of fitting here shown is that it iscompletely flush with the panel face, presenting a smooth surface for asuperposed panel (Fig. 4).

We claim: e

The method of making a concrete building member comprising, casting aconcrete base layer, sealing the exposed top surface of said layer bycoating with a liquid sealing composition containing a substantiallywater-insoluble i'llmforming substance in an evaporable liquid vehicle,whichisubstance, upon removal of the liquid vehicle will deposit on theconcrete layer as a uniform, substantially water-impermeable and easilyseparable sealing film which will prevent formation of a bond betweenthe concrete of the base layer and concrete poured wet upon such adeposited sealing film and set and cured thereon, casting a wet concretelayer on the exposed coated surface of the base layer after said baselayer has at least partially set, thereby producing a superposedconcrete layer on the coated and at least partially set base layer, thelayers being separated by said film, permitting the superposed concretelayer to set and cure in its position on the sealing film until the thusproduced building member has attained sufficient strength to be liftedfree of the base layer, and then removing the produced building memberfrom the base layer.

JAMES ED MCCLELLAN. JACK H. MAcDONALD.

REFERENCES CITED The following references are of record in the ille ofthis patent:

UNITED STATES PATENTS Number Name Date 712,841 Parmley Nov. 4, 19021,066,436 Peltzer July 1, 1913 1,168,492 Freund Jan. 18, 1916 1,326,400Halverson et al. Dec. 30, 1919 1,394,255 Davis Oct. 18, 1921 1,412,392Earley Apr. 11, 1922 1,942,000 Reynolds July 1, 1931 2,081,499 Nagel May25, 1937 2,143,515 Hayden Jan. 10, 1939 2,199,533 Wuellner May '7, 19402,235,001 Allen Mar. 18, 1941 2,275,272 Scripture, Jr. Mar. 3, 19422,293,410 Sorem Aug. 18, 1942 2,306,107 Henderson Dec. 22, 1942 2.., nLaub

